Field of the Invention
The present disclosure relates to a display device and a method of manufacturing the same. More particularly, the present disclosure relates to a thin film type back light unit for a flat panel display device.
Discussion of the Related Art
Nowadays, liquid crystal display (LCD) devices are widely used for display applications such as portable computers, notebook PCs, office automation devices, audio/video devices, advertising displays for indoor or outdoor, and so on. A typical transmittive type LCD device displays an image by modulating the luminescence of the light incident from the backlight unit by controlling the electric field applied to the liquid crystal layer.
There are typically two types of back light unit: a direct type and an edge type. The direct type back light unit has a structure in which a plurality of optical sheets and a diffusion plate are stacked under the liquid crystal panel and a plurality of light sources are disposed under the diffusion plate.
FIG. 1 is a cross-sectional view illustrating a structure of an LCD device having a direct type back light unit including a light emitting diode (LED) array as a light source according to the related art.
The direct type back light unit DBLU includes a light source disposed under a liquid crystal panel LCDP and radiating a back light directly to the liquid crystal panel LCDP. The light source may be a thin fluorescent lamp. Alternatively, as shown in FIG. 1, the light source may be an LED array LEDAR having a lower power consumption and enhanced luminescence.
The LED array LEDAR is disposed in a matrix on the bottom surface of the case CASE. The case CASE may be installed at the cover bottom CB. In some cases, the case CASE may be omitted, and the LED array LEDAR may be disposed at the cover bottom CB directly. On the LED array LEDAR, a diffusion plate DIFF is disposed. The diffusion plate DIFF diffuses the back light from the LED array LEDAR to provide an evenly scattered back light over the light incident surface of the liquid crystal panel LCDP. Between the diffusion plate DIFF and the liquid crystal panel LCDP, a plurality of optical sheets OPT may be disposed. The optical sheets OPT include one or more prism sheets, one or more diffusion sheets, and/or a dual brightness enhancement film (or DBEF). The prism sheets converse the scattered and/or diffused back light by the diffusion plate DIFF to the liquid crystal panel LCDP for enhancing the brightness of the back light. The diffusion sheets diffuse again the conversed back light by the prism sheets over the liquid crystal panel LCDP to have an evenly distributed luminescence.
A guide panel GP wraps and/or surrounds the side surfaces of the liquid crystal panel LCDP and the direct type back light unit DBLU, and supports the liquid crystal panel LCDP by being interposed between the liquid crystal panel LCDP and the optical sheets OPT. The cover bottom CB wraps and/or surrounds the case CASE and the bottom surface of the direct type back light unit. On the bottom surface of the case CASE having the LED array LEDAR, a reflective sheet REF is disposed to reflect the back light leaked from the diffusion plate DIFF and/or the optical sheets OPT to the liquid crystal panel LCDP. The top case TP surrounds the upper edge of the liquid crystal panel LCDP and the side surface of the guide panel GP.
In the meantime, the edge type back light unit may have a thinner thickness than the direct type back light unit. Currently, LCD devices have typically an LED light source rather than a fluorescent lamp. Due to easy installation of the light source, the edge type back light unit is more widely applied to various types of LCD devices, in which a plurality of LED light sources are disposed at a side surface of the liquid crystal panel.
Hereinafter, referring to FIG. 2, the edge type back light unit will now be described. FIG. 2 is a cross-sectional view illustrating a structure of an LCD device having an edge type back light unit including a light emitting diode array as a light source according to the related art.
Referring to FIG. 2, the edge type back light unit comprises a cover bottom CB, a light guide LG disposed at a bottom surface of the cover bottom CB, and a light source disposed between the side surface of the light guide LG and the cover bottom CB and providing a back light to the side surface of the light guide LG.
The light source may be a thin fluorescent lamp. Alternatively, as shown in FIG. 2, the light source may be an LED array LEDAR having a lower power consumption and enhanced luminescence. The light source may be disposed at the side surface of the light guide LG using an installing means such as a housing. The light guide LG receives the back light from the LED array LEDAR and refracts the direction of the back light as being perpendicular to the light incident surface of the liquid crystal panel LCDP. Between the light guide LG and the liquid crystal panel LCDP, a plurality of optical sheets OPT are disposed. The optical sheets OPT include one or more prism sheets, and one or more diffusion sheets for scattering and/or diffusing the back light from the light guide LG. To enhance the brightness and/or luminescence, the optical sheets OPT may further include a dual brightness enhancement film (or DBEF).
The guide panel GP wraps and/or surrounds the side surfaces of the liquid crystal panel LCDP and the edge type back light unit, and supports the liquid crystal panel LCDP by being interposed between the liquid crystal panel LCDP and the optical sheets OPT. Between the cover bottom CB and the light guide LG, a reflective sheet REF is disposed to reflect the back light leaked from the diffusion plate DIFF and/or the optical sheets OPT to the liquid crystal panel LCDP. The top case TP surrounds the upper edge of the liquid crystal panel LCDP and the side surface of the guide panel GP.
As described above, an LCD device, which is a non-self-luminance display, typically has a back light unit. The back light unit is desired to direct the back light evenly distributed over the whole surface of the liquid crystal panel. As such, various optical devices and/or means are typically used to transform a light from a point light source or a line light source to a light from a plane light source. Due to the optical characteristics and structures of these optical devices and/or means, the back light unit is typically ended up with some thickness. Even though flat panel display devices such as LCD devices have a remarkably slimmer profile than conventional display devices such as cathode ray tubes, more advanced technology for developing a new back light unit suitable for a slimmer and lower power consumption display device is desired.